These are repurposed mining “cards”. You can get them on the used market. I got mine from ebay, but aliexpress has them too.

Right, they are originally mining cards, but there is a community turning them into living room PCs with 3d printed cases. It is very much a DIY project, but there are also premade kits available.

https://media.printables.com//media/prints/1499974/rich_content/fc4dd779-afb9-434f-8a03-aa6949592e16/thumbs/inside/1280x960/jpg/img_20251128_182707_270-9.webp

Or a BC-250. Same chip, just with fewer cores. Performs about the same as a ryzen 2600 + rx 6600 pc.